Sunday 26 April 2020

For Sale: Flatslide carbs for XS750/850 Triples

Well you guessed it, now that the Gixxer-flatslides are on the sidecar the XS Triple flatslides are for sale.

They come with two sets of cables, one is new and the other one is the one I used for the last two years or so.

If you're interested send me a mail or contact me via Instagram.

Price: 500 Euros

Tuesday 21 April 2020

The XS Triple Sidecar - gets some second hand GSXR 750 flatslides (addendum)

I had a quick hour in the workshop this morning and turned the idle adjuster down a bit, so that the spring wouldn't bottom out as that allowed me to get the old girl to idle and then sync the carbs.

With the spring base back another three or four milimetres, I can now screw the adjuster in far enough to set the idle properly. 

Only #1 carb was really a wee bit out of sync, #3 was more or less good from the get go. 

And thanks to all of that the old girl now has got a very grumpy idle...

Time for a testride, I'd say - but to make starting a bit easier, maybe first prepare the choke-rod and grind some dimples in it, so it would lock in place.

Secretly, this is my favourite shot of the whole build - safety-wired the fuel lines to the bodies as they were leaking ever so slightly. 

As the throttle housing is from a DR600 and would normally be flipped the other way round, I had to tap the hole in M5 and bolt it up. It makes a perfect point for oiling the cables though, so I guess I won't weld it up.

First testride went very reasonable. Lots of low-down torque, after adjusting the mix-screws a bit leaner there was perfect pickup from very low revs, but after a few kilometres #3 cylinder didn't want to fire anymore. Turns out the needle-jet is only a slide fit and not a press-fit anymore in its bore and I didn't notice screwing the mainjet into thin air, when I (hastily) assembled the carbs for a first testride.

So what's the verdict: Lots of grunt, which is exactly what I was after. I have to play around and maybe order some more mainjets as the full-throttle performance leaves some room for improvement. Brakes and suspension are working fine after the cleanup and overhaul, but the number of oil-leaks is starting to become a real issue. Guess I'll get by another season, but I really should have a look at the other engine-block I have and start tackling that one.

Saturday 18 April 2020

The XS Triple Sidecar - gets some second hand GSXR 750 flatslides

The plan is simple: Take carbs from an inline-four, remove one carb, put it back together, job's a good un'. Yeah right. What you see is a week's worth of work.

So I started off with a set of perfectly good GSX-R 750 carbs.

Removed the rails and the right-most carb to get a feeling, if and where the carb bodies needed to be modified and if maybe the stock throttle shaft could be repurposed.

This would have been my preferred placement for the throttle cables and idle-adjuster as they would have been perfectly accessible...

... and perfectly in the way of the fuel tank.

So shuffled the carbs around, ran the throttle cables through the frame. (Thanks Yamaha for placing this opening in just about the right spot!)

With the carbs laid out and all clearances checked, the carb spacing was finalised (88mm for those who want to do similiar things) and 15x15x2 stainless L-profile was drilled.

And it turns out there's just one spot, where things get a bit tight. Removing about 2mm from this fuel-line boss was all it took to make them clear.

In order to get the spacing on the bottom rail right, the throttle-shaft (10mm) was cut from a bit of stainless. (Stupid idea, more on that later.)

The bottom rail was then laid out and pockets milled out for the mixture-screws and the profile shortened on the engine side, so access would be a bit easier.

Drilling stainless is a royal pain. Even more so, when you have a slightly worn out Chinese drill chuck, which has got a bit of a death-wobble to it. (Unfortunately my good chuck won't grip drills smaller than 3mm and the one in the picture is a 2.0mm one...) So it broke off flush with the shaft.

Nevermind, got it out and went ahead tapping the shaft...

... bugger.

Then I went to my metal supplier and got an offcut of silversteel, enough for two carbs. Let's just say I am happy I did and the following pictures show me working with the material for the second shaft made from silversteel ...

Old machinist's trick here on how to find center, if you don't have a DRO on your mill (or want to do it quicker with just a long metal ruler) - once you've found center the ruler will be perfectly parallel to the mill's table. The longer the ruler the more accurate the measurement.

Throttle assembly is off a DR600, including the cables. These are actually bits I bought many years ago for my XT500.

And that's the carbs more or less finished. (Chokes missing in the pictures below, also the idle adjustment needs some quality time with my lathe and of course the whole lot has to be synced.)


This is the actual second start of the XS with the carbs installed. No sync, no idle adjustment, nothing and she just purrs like a kitten.

What's left to do: Fix the idle adjustment, sync the carbs and then probably throw the O2-sensor on and see where we're at. First testride (regardless of mal-adjusted carbs) has shown a substantial increase in low-end torque, which is all this exercise has been about.

Saturday 11 April 2020

The XS Triple Sidecar - Spring cleanup and brake overhaul

With the sidecar bearing most of the weight of my Winter-time motorcycle commutes, Spring clean is as much about cleaning as it is about taking inventory of the damages that have amassed by the same and subsequently identify areas that need work.

Once again, the protective wax I used has done an admirable job of keeping rust at bay and mostly there have been no real shortcomings to report, aside from the brakes.

When I built the sidecar, I overhauled the brakes with all new seals and stainless steel brake pistons. I was a bit shocked to find out that the dust seals had completely disintegrated and were due for replacement after only two or three seasons.

Plenty of brake-lube (type of petroleum jelly), prevented the worst.

And that's why you want stainless steel brake pistons, even after sitting in the salt they come out immaculate again.

The old seals were thin like paper and about as solid as rotten wood.

In the course of the whole job, I also swapped out the brakepad retainer bolts for stainless items with a hex on the outside. I kept them well lubed with copper-slip, but this allows me to actually use a ratchet to install and remove them.

Note a certain German supplier for SR&XT parts has got them as the original Yamaha bolt is no longer available.

With the stopping side of things sorted out, it was time to focus a bit more on the going faster side of things. As the casual observer might have noticed before, I am a huge proponent of using O2-sensors for fine-tuning carburettors. Now when I built the exhaust for the XS Triple, I did install an O2-bung, but for some unknown reason, I must have slipped an a bit of exhaust tube got in the way plus the thread of these cheap O2-bungs isn't exactly true to the specification. After a bit of die-grinder and tapping action, I was for the very first time able to monitor live, what was actually going on under load.

Yes, that reads as 13.9:1, really more a wonder I haven't burned any holes into my pistons yet. The mix-screws on these carbs are incredibly sensitive, so a 1/4-turn bumped me straight into the high 12s, which instantly meant black skidmarks in the driveway. 

You have to give the sidecar credit though, put an old car-battery on the chair, hooked everything up and off you go. (Turns out, the stock reg/rect unit is so noisy, the electronics in the wideband controller were (not very politely) showing me the middle finger.

Why fix this now, when I obviously have the carbs already dialed in somewhat satisfactory? Well, here's a bit of a project outlook for you.

Mikuni VM29SS out of a 1986/1987 GSXR 750 slabbie. They'll need a sh*t-ton of tweaking to fit and I just know I will be cursing myself for using them. But they've got accelerator pumps, are a slightly smaller diameter (29mm vs. 33mm) and I have quite a bit of hands-on-experience with them from installing them on (my) Kawasaki Zeds.